A control program, in which a control operation of a vehicle-mounted control device mounted on a vehicle is described, is stored in a non-volatile memory such as a flash memory in a microcontroller. Data used in the control program, such as initial values or the like, are also stored in the non-volatile memory. It is usual that these programs or data are not changed after vehicles are shipped to markets. However, upon detection of bugs or for providing a better service, the control program or data is updated.
As for update processing of the control program or data of the vehicle, the vehicle is brought to a dealer and a rewrite is performed therein. However, in recent years, there has been proposed a method of performing update processing through a wireless communication such as a mobile telephone network that is an infrastructure outside the vehicle.
In PLT 1, an information management base station device outside a vehicle transmits an update request to a stopped vehicle through a wireless communication device mounted on the vehicle, and the vehicle receiving the update request wakes up from a sleep state, starts up a vehicle-mounted control device mounted on the vehicle, and writes an updated program transmitted from the information management base station device to the vehicle-mounted control device.
Also, in PLT 2, an external tool and a writing device mounted on a vehicle are connected to each other through a communication cable, an updated program transmitted from the external tool is stored to the writing device, and then, the updated program is written from the writing device to a vehicle-mounted control device in a state in which the communication cable is disconnected therefrom.